Letter Contract AF 32(038)-22617 of March 1951 had originally called for the production of 250 B-57s, but it was amended several times. In the agreement of August 11, 102 B-57Bs were substituted for 70 B-57As and for 32 RB-57As. In Letter Contract AF 33(600)-22208, which was issued on September 19, 1952, 119 more B-57Bs were added. It was amended on December 18, bringing the Fiscal Year 1953 B-57B procurement to 191, and bringing the planned total production of the B-57B to 293.
However, the production order was not to remain at that level. In early 1954, the USAF cut back the FY 1953 B-57B procurement to 158 (a 33-aircraft reduction) and dropped the tentative order for 50 more. In the spring, 38 additional B-57Bs were cut in favor of an equal number of B-57C dual-control trainers. A few months later, 20 additional B-57Bs were diverted to the B-57D program, bringing the total reduction to 91 aircraft In the event, a total of 202 B-57Bs were built, more than all the other versions put together.
The most significant change introduced by the B-57B was the complete redesign of the cockpit area. The navigator/bombardier was moved from the "buried" position in the fuselage behind the pilot and moved upwards to a position behind the pilot, with both crew members seated in tandem underneath a large clamshell-opening bubble canopy. This arrangement improved visibility, provided more space for equipment, and made it easier for the navigator/bombardier to escape from the aircraft in the event of an emergency. The new arrangement also made for better communication between the two crew members. Although the pilot's seat was on the aircraft centerline, the navigator's seat was lightly offset to left of center to provide room for a Shoran receiver-indicator and the M-1 toss-bomb computer unit. The B-57B also introduced a flatplate windshield which permitted the installation of a gunsight, which was impossible in the B-57A because of the distortion and flexing of the latter's curved one-piece canopy. The tandem cockpit seating arrangement was first tried out on Canberra WD940, but it is not certain if the aircraft was ever actually flown in this configuration. The first true B-57B flew on June 18, 1954.
Four external pylons were fitted underneath each wing that could carry bombs or rockets. A 17-foot long, one-piece rotating bomb door was incorporated, which was a feature originally developed for the XB-51. The door rotated 180 degrees around two pivots, taking four seconds to open and six to close. The bombs were attached directly to the inward side of the door, so that when the door was rotated open the bombs were in an externally-mounted position. The attachment points on the door allowed a wide variety of stores to be carried, including nuclear weapons. The rotating door also made it possible to make bombing runs at higher speeds because the buffeting associated with conventional bomb doors when they were opened was eliminated. The development of this door was the main reason why the B-57 became the most accurate of the aircraft using the LABS. Another advantageous feature was that the entire door could easily be removed from the aircraft while it was on the ground, making it possible to pre-load the door with ordnance and quickly winch it into place inside the fuselage, enabling a rapid turnaround.
An APW-11 Bombing Air Radar Guidance System was provided, helping the pilot to make accurate runs into the target. The Shoran bombing system was added for use by the bombardier/navigator. An APS-54 Radar Warning System was provided, which increased the angle of coverage astern of the aircraft and gave the crew some warning of AI illumination.
There were important changes to the starter system, with the manually-operated cartridge of the RB-57A being replaced by one that was electrically-ignited. A pyrotechnic cartridge was loaded into a breech in the center of the engine air intake. When ignited, the cartridge drove a starter turbine which brought the engine up to a self-sustaining rpm via a clutch system. This eliminated the need for heavy and bulky ground starting units, but the starter cartridge spewed out a characteristic dense cloud of choking black smoke, which was often mistaken by inexperienced ground crews for an engine fire.
The new B-model had a set of speed brakes installed at the waist position of the fuselage. It was found that the finger-like spoilers on the top and bottom of the outer wing panels did not provide sufficient drag for speed control, and these were supplemented by the waist speed brakes. It would turn out that the speed brakes would be very useful in controlling acceleration during diving passes in the ground attack role.
Some other features incorporated on the B-57B worth mentioning are wing surface and engine inlet anti-icing, anti-skid wheel brakes, a drag chute for landing on short runways, and power boost controls.
A forward-firing armament was fitted to the B-57B. The B-57B initially mounted eight 0.5-inch machine guns, four in each wing in pairs outboard of the engine nacelles. Each wing carried 300 rounds of ammunition. After the 83rd B-57B (52-1575), the eight 0.50-inch forward-firing machine guns in the wings were replaced by four M-39 20-mm cannon, two in each wing. The cannon were fixed to fire downwards at 3.5 degrees from the flight path. Each gun had 290 rounds of ammunition. The mounting of cannon in place of machine guns involved airframe alteration and considerable wing modifications. Consequently, machine-gun equipped B-57Bs were not converted to the cannon weapons.
According to the original licensing agreement with English Electric, the name Canberra was also to be used to describe the Martin-built version of the British-designed twin-jet bomber, both by the Glenn L. Martin Company itself and also by the US Air Force. Although the official popular name of the B-57 was indeed listed as Canberra by the Air Force, this name was not used very often in practice, the aircraft being referred to simply as B-57.
The first few B-57Bs to be built had a natural metal finish, but the remainer were finished in gloss black overall, in fitting with their night intruder role.
The first true B-57B flew on June 18, 1954. The first organization to re-equip with the B-57 was the 345th Bomb Group (Tactical), based at Langley AFB in Virginia. The 345th was initially responsible for training its own crews. However, in the spring of 1955 a special B-57 operational conversion unit was formed--the 3510th Combat Crew Training Wing (CCTW) at Randolph AFB in Texas. Shortly thereafter, a second B-57B unit, the 461st Bomb Group (Tactical) was formed at Hill AFB in Utah, receiving its first B-57Bs in January of 1955. In the summer of 1955, they moved to Blytheville AFB in Arkansas. The 461st BG was, in fact, the first of the Bomb Groups to be fully equipped with B-57s.
B-57B units were also formed overseas. In 1956, the 38th Bomb Group (Tactical) was formed at Laon AB in France. The 3rd Bomb Group in the Far East at Johnson AB in Japan traded in its B-26s for B-57Bs in 1957.
From the beginning, emphasis was placed on rapid deployment of the B-57B overseas in the event of a crisis. Tactical cooperation procedures were worked out in late 1956 in Exercise Sagebrush, which involved joint operations by the 461st BG and the RB-57As of the 363rd TRW and was carried out across the southeastern portion of the USA. The 461st TBG and the 363rd TRW were the aggresors in the exercise. In 1957, 13 B-57s of the 461st BG embarked on a goodwill tour of Latin America, after which it deployed to Laon in France to fly alongside the 38th BG in Exercise Counter Punch, NATO's annual tactical air exercise.
Like the RB-57As, the B-57Bs suffered from engine malfunctions which filled up the cockpit with toxic fumes, which led to a brief grounding. The culprit turned out to be the engine compressor, which was quickly fixed and the grounding order was lifted. Difficulties with the aircraft's stabilizer control system led to another grounding order in February of 1955. The B-57Bs were released for flight a month later, but were restricted to a maximum speed of only 250 knots pending the modification of the horizontal stabilizer and the installation of a different stabilizer trim switch.
During this period a number of B-57Bs were lost in accidents, particularly during high-speed, low-level operations when aircraft suddenly and unexplainedly dove into the ground. As these accidents persisted, all tactically-assigned B-57Bs were grounded again in May of 1956 for a period of four months while the problem was investigated. The fault was eventually traced to a faulty tailplane actuator which set the trim incorrectly. The installation of a new actuator switch cured the problem.
The USAF was not very happy with the B-57B as it was initially produced. It was still deemed to be inadequate to meet the night intruder and close support role for which it had originally been designed. The target acquisition system was inadequate, the navigational range was too short, and the radio navigation could not recover the aircraft after strikes. The armament was inadequate--the gun-bomb-rocket sight, the gun charging systems, and the external stores release mechanisms were all unreliable. In September 1955, the Air Force organized a three-phase program to bring the B-57B up to tactical standards. Phase 1 installed the low altitude bombing system (LABS), the AN/APS-54 Search Radar, and the ALE-2 chaff dispenser. Phase 2 added the M-1 toss bomb computer and the AN/APG-31 tie-in equipment. This phase also involved modifications to the longitudinal control and stabilizer systems and to the fuel control panels and special weapon bomb bay doors. Phase III dealt with the AN/APN-59 radar beacon, which was destined never to be installed. These modifications were carried out by Martin subcontractors in the USA and overseas. These modifications were still in progress in late 1957.
The service life of the B-57B with USAF tactical bomb groups was destined to be brief. After three years of service with the B-57s in tactical bomb groups, the decision was made to phase out the B-57 in favor of supersonic aircraft. By the end of 1957, the tactical squadrons of USAFE had began to re-equip with the F-100 Super Sabre, and early in 1958, the 38th BG returned to the USA to begin deactivation. In April of 1958 the 461st BG began to deactivate at Blytheville AFB. As the active duty USAF TAC bomb groups deactivated, their aircraft were transferred to the Air National Guard (ANG)
The 345th BG was about to deactivate at Langley AFB when one of its squadrons had to be hastily deployed in July of 1958 to Incirlik Air Base in Turkey to make a show of force in response to a crisis in Lebanon. They stayed there three months. After the Lebanon crisis was defused, the B-57Bs were returned to Langley AFB.
The deactivation of the 345th BG was further delayed by a crisis in the Taiwan Straits. In August of 1958, Mainland Chinese forces began bombarding the Nationalist-held island of Quemoy. In late August, the 345th BG sent a detachment of B-57Bs to Okinawa to stay on alert just in case mainland forces tried to invade Taiwan. The 3rd BG stood by in Japan to strike strategic targets in China, North Korea and possibly even the Soviet Union should the crisis escalate out of control. Fortunately, the crisis soon cooled and hostilities were averted, and the 345th BG returned to the USA to begin deactivation. This was completed in June of 1959.
This left the 3rd Bombardment Group based in Japan as the sole active B-57 USAF unit. Since nuclear weapons could not be stationed in Japan, in August of 1958, the 3rd BG set up a rotation of crews to stand nuclear alert at Kunsan (K-8) air base in Korea. This rotation continued until April of 1964, when the 3rd BG returned to Yokota to begin the process of inactivation.
This would ordinarily have been the end of the service of the B-57B with the USAF, with the 3rd BG being inactivated and all its planes being transferred to the Air National Guard. However, the worsening situation in Indochina led to orders for the 8th and 13th Bomb Squadrons of the 3rd BG to deploy to Clark AFB in the Philippines for possible action in Vietnam. As it happened, this move did not take place until August 5, following the Gulf of Tonkin incident in which North Vietnamese gunboats clashed with US destroyers.
According to the initial plan, 20 B-57Bs of the 8th and 13th BS were to be deployed to the Bien Hoa air base near Saigon. This would mark the first deployment of jet combat aircraft to Vietnam. This was technically a violation of the Geneva Protocols which forbade the introduction of jet combat aircraft to Vietnam, but the Gulf of Tonkin resolution which had just been passed by Congress was taken as a pretext to remove all such restrictions.
The initial deployment to Vietnam got off on the wrong foot. The first two B-57Bs to land collided with each other on the ground and blocked the runway at Bien Hoa, forcing the rest of the flight to divert to Tan Son Nhut Airport on the other side of Saigon. One of the B-57Bs dived into the ground during approach at Tan Son Nhut and was destroyed, killing both crew members.
During the next few weeks, more B-57Bs were moved from Clark AFB to Bien Hoa to make good these losses and to reinforce the original deployment. Things got so crowded at Bien Hoa at that time that some of the B-57s had to be sent back to Clark AFB. Initially, the B-57Bs were not cleared for actual combat missions, the aircraft being restricted to unarmed reconnaissance missions that were mainly designed to boost the morale of the population.
However, actual combat was not to be delayed very long. On November 1, 1964, Viet Cong squads shelled the airfield at Bien Hoa with mortars, destroying five of the B-57s parked there and damaging 15 others. Further Viet Cong mortar attacks led General William Westmoreland on February 19, 1965 to release B-57Bs for combat operations. The first such mission took place on that same day, a strike against suspected Viet Cong guerillas near Bien Gia, about 30 miles east of Saigon. This strike was, incidentally, the first time that live ordnance had been delivered against an enemy from a USAF jet bomber.
The B-57Bs hit North Vietnamese territory for the first time on March 2, some 25 miles north of the DMZ. This was the first of a series of interdiction strikes that came to be known as *Rolling Thunder*. The usual bomb load on these operations was nine 500-lb bombs carried in the main weapons bay and four 750-lb bombs on the underwing pylons.
In April of 1965, B-57B crews began night interdiction strikes against enemy supply lines along the Ho Chi Min Trail. Operations were carred out in cooperation with C-130 or C-123 flare-deploying aircraft that illuminated potential targets and with USMC EF-10B Skyknight electronics warfare aircraft that jammed radar-controlled AAA and detected enemy missile sites that were preparing to launch.. Eventually these night interdiction missions extended into North Vietnam, the first such attack taking place on April 21, 1965. However, it was considered too dangerous to fly C-130 flare-deploying aircraft into North Vietnamese airspace, so each B-57B carried a set of MK-24 flares in addition to bombs.
On May 16, 1965, while waiting to takeoff on a mission, a B-57B exploded on the ground at Bien Hoa, setting off a whole chain of secondary explosions. The resulting conflagration destroyed ten B-57s, eleven VNAF A-1H Skyradiers, and a US Navy F-8 Crusader. The surviving B-57s were transferred to Tan Son Nhut and continued to fly sorties on a reduced scale until the losses could be made good. Some B-57Bs had to be transferred to Vietnam from the Air National Guard, and 12 B-57Es had to be withdrawn from target-towing duties and reconfigured as bombers to make good these losses.
In June of 1965, the 3rd Bomb Group moved to Da Nang to carry out night interdiction operations over North Vietnam and Laos. Principal targets were trucks, storage and bivouac areas, bridges, buildings, and AAA sites. When deployed at Da Nang, the 8th and 13th Squadrons came under operational control of the 6252nd Tactical Fighter Wing which became the 35th TFW about a year later.
Combat attrition in the B-57 force plus the increasing availability of higher performance fighters to carry out the air war against the North caused the 3rd BG to be withdrawn from operations against the North in October of 1966 and relocated to Phan Rang, just south of Nha Trang and Cam Ranh Bay. It carried out attacks against Communist forces in the Central Highlands and supported US ground troops in the so-called "Iron Triangle". While there, the B-57s operated alongside the Canberra B.20s of No 2 Squadron of the Royal Australian Air Force.
In January of 1968, the 13th Bomb Squadron was deactivated, and the 8th BS was left in permanent residence at Phan Rang. The main emphasis was again on night interdictions against the Ho Chi Minh Trail. By July of 1969, the 8th BS's strength was down to only 9 aircraft, and it was decided that it was time to retire the B-57B from active service. The surviving aircraft were sent back to the USA in September and October and put into storage at Davis Monthan AFB. The identity of the 8th BS was transferred to another unit at Bien Hoa to become the 8th Attack Squadron, which was equipped with Cessna A-37s.
Out of the 94 B-57s that were assigned to the Southeast Asia theatre, 51 were lost in combat (including 15 destroyed on the ground). 11 were withdrawn early to support the B-57G program.
Engines: Two Wright J65-W-5 turbojets, 7220 lb.s.t. each Performance: Maximum speed 598 mph at 2500 feet, 575 mph at sea level. Cruising speed 476 mph. Stalling speed 124 mph. Combat ceiling 45,100 feet. Initial climb rate 6180 feet per minute. Combat radius 948 miles with 5240 pounds of bombs. 2722 miles ferry range. Weights: 27,091 pounds empty, 53,721 pounds gross, 36,689 pounds combat weight. Dimensions: Wingspan 64 feet 0 inches, length 65 feet 6 inches, height 14 feet 10 inches, wing area 960 square feet. Armament: Four 20-mm M-39 cannon in the wings, 290 rounds per gun. 4500 pounds of bombs in internal bomb bay, 2800 pounds underwing.
52-1493/1594 Martin B-57B-MA 53-3859/3935 Martin B-57B-MA 53-3937/3939 Martin B-57B 53-3941/3943 Martin B-57B 53-3945/3947 Martin B-57B 53-3949/3962 Martin B-57B 53-3983/4015 Martin B-57 - All cancelled.